Responses of threespine stickleback (Gasterosteus aculeatus, L) transcriptome to hypoxia

Area of Science:

• Environmental Science
• Aquatic Biology
• Molecular Biology

Background:

• Hypoxia, or low oxygen, is a natural aquatic phenomenon exacerbated by human activities like eutrophication and climate change.
• Threespine stickleback (Gasterosteus aculeatus) is a valuable model organism for ecological, evolutionary, and physiological research.

Purpose of the Study:

• To investigate the physiological and transcriptomic responses of threespine stickleback to acute hypoxic stress.
• To identify specific genes and molecular pathways affected by hypoxia in this species.

Main Methods:

• Threespine sticklebacks were exposed to controlled hypoxia (24-28% air saturation) and normoxia for 3 and 48 hours.
• Transcriptomic analysis was performed using microarrays for 48-hour treatments.
• Real-time quantitative PCR (RT-qPCR) was used to validate selected gene expression changes at both time points.
• Ethoxyresorufin-O-deethylase (EROD) activity was measured to confirm protein-level changes.

Main Results:

• Microarray analysis indicated downregulation of genes involved in cell proliferation, DNA replication/repair, and protein degradation under hypoxia.
• Upregulation of genes encoding oxygenase and oxidase activities, including two 2-oxoglutarate-deoxygenases (JMJD6 and JMJD2C), was observed.
• JMJD6 transcription changes in response to hypoxia were characterized for the first time.
• Increased Cyp1A2 mRNA levels were confirmed at the protein level via EROD activity.

Conclusions:

• Hypoxia significantly impacts gene expression in threespine stickleback, affecting fundamental cellular processes.
• The study highlights the role of specific oxygenase enzymes, like JMJD6, in hypoxic adaptation.
• These findings provide insights into the molecular mechanisms of hypoxia tolerance in aquatic organisms and support the use of threespine stickleback in physiological studies.